1. Field of the Invention
The present invention relates to an electroluminescent display panel, and more particularly to the one which is able to display images in different colors according to situations where the display is used.
2. Description of Related Art
An example of the electroluminescent display panel of this kind is disclosed in JP-A-58-30093. In this display panel, a first luminescent layer of ZnS:TbF.sub.3 for displaying images in green and a second luminescent layer of ZnS:SmF.sub.3 for displaying images in red are laminated, with an insulation layer and an intermediate electrode disposed therebetween. When voltage is imposed on only the first luminescent layer, images are displayed in green, when voltage is imposed on only the second luminescent layer, images are displayed in red, and when voltage is imposed on both luminescent layers, images are displayed in a lemon color which is a mixture of green and red.
This kind of display panel is suitable for use as an instrument panel for an automobile, which is able to display images in different colors in day time and in night time. Generally, it is desired to display images with a high luminance in day time, while it is desired not to display images in colors which include red in night time because red is a warning color and a driver feels uneasy with it. The display panel disclosed in the publication above is able to display images in red or lemon with a high luminance in day time by imposing voltage on both first and second luminescent layers, and to display images in green in night time by imposing voltage only on the first luminescent layer. Thus, the display panel fulfills the general requirement. However, it is necessary to provide an intermediate electrode between the first and second luminescent layers. The intermediate electrode makes the structure complex, and accordingly the display panel becomes expensive.